Hog Boys Boardtrack Racer

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stocksucks

stocksucks

New Member
May 23, 2012
32
0
0
Portugal
Hey there.
Iv'e been building this boartrack racer bike for a while now, and some changes have been made as it evolves. You guys can check out all the process at http://www.ratrodbikes.com/forum/viewtopic.php?f=54&t=33749&p=538665#p538665.

This is it's actual state:








Now I've got a problem!
I'm using a Lombardini 4 stroke 252cc engine and it has a conical engine shaft, not suited for the straight keyway of my centrifugal clutch.
So i'm stuck with a 11 teeth sprocket, from which I will have to run a chain to a 26 teeth input sprocket on a jackshaft. On the other end of the jackshaft will be my centrifugal clutch, runnin a chain to a final 35 or 44 teeth sprocket.
Here's a sketch:



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The problem is that I dont know if the shaft will acquire enough rpm for the clutch to engage, since the 11t to 26t arrangement gives torque, not speed. This would be reached with the final 11t to 44t setting.

Could someone do the math for me and tell me what will happen?
If it does not work what arrangement would be advised?

Thanks a lot and keep it up.
 
stocksucks

stocksucks

New Member
May 23, 2012
32
0
0
Portugal
Hey there.
Thanks for the compliments guys.
@RustyCase: kill switch very easy to fabricate. See link for detail.
@VeniceMotorBikes: I'm not planning on using any pedals. I did, at start, but those double coasters / sprockets are'nt much available around here, and also I like to build things with whatever I have laying around...
So what do you think? Can I go with the arrangement drawn?
Should I go for a belts system?
Thanks and keep it up!
 
Bigboy

Bigboy

New Member
May 4, 2011
195
6
0
Placerville, California.
The Jack-shaft will turn to slow to engage the clutch!
We would recommend 11t on the input on the jack shaft as well and
adjust you "driving needs" on the rear once you know the character of the engine.
Torque should not be an issue with 252cc with proper carburetor and
correct exhaust (length!! and back-pressure) .
 
stocksucks

stocksucks

New Member
May 23, 2012
32
0
0
Portugal
Thanks for helping guys.

@ VeniceMotorBikes: The rear hub is not a freewheeler, but I cannot run a direct chain, because the alignement is way off due to the engine's size. Also I planned to use a jackshaft so the frame was built that way. I had a direct drive with a previous engine, a 147cc 4 stroke villiers (11teeth to 44 on the rear). With this setting I managed to some 37mph, but it did not have any power at take off. See video:http://www.youtube.com/watch?v=fL26UnAN8zE

@Bigboy: That's what I'm affraid of, I guess that the output on the jackshaft will have torque but not enough rpm to engage. I can always mess with the clutch's springs, but it's not an "accurate science"!
The carburetor i'm using is not meant for that engine. In fact i'm using a 19 diam. from a 350cc engine (same brand only larger), instead of the 17 diam. it originally used. It's a gas sucking devil!

So.. do you guys think that I can go 11T X 11T X11T(clutch) and then adjust torque on the final sprocket on the rear wheel?

Thanks a lot and keep it up.
 
professor

professor

New Member
Oct 14, 2009
500
1
0
Buffalo ny area
Somewhere, you need to deepen the ratio. All those 11s will not work without a really BIG rear sprocket. I think most cent. clutches for low rpm 4 stroke engines engage at around 2000 rpm.
Come to think of it- a guy here sells a reduction unit/ clutch that has the clutch in the position you suggest, do a search on "q-matic".
The clutch is a Maxtorque unit with special springs I suppose.
They were also talking about rear sprockets of 56 to 72 teeth for varied uses.
So your idea looks doable with some reduction between the engine sprocket and the jackshaft, but you will need a real low (light) spring in the clutch.
Personally, I want to get away from chain drive - like the real old motor bikes that had a pulley attached to the rear rim. That would sure give you some reduction.
 
M

monark

New Member
Feb 1, 2012
87
0
0
sweden
hello portugal! you got a real good eye for lines,nice work. hope you find a solution to the drivetrain issue (gona be in the same place myself soon).me likey!!
 
stocksucks

stocksucks

New Member
May 23, 2012
32
0
0
Portugal
Hey there guys.
Glad you liked it monark. I'll have a new video on as soon as I get it runnin..
Thanks for helping professor! I know I need to work on that arrangement. That was the initial jackshaft idea all along. I'm gonna look at that tip you gave about the q-matic, but I really like the belt transmission idea.
Being a newby to this site, could you point out one or two belt driven bikes that I can look up to in order to grab some ideas?
Thanks a lot
 
stocksucks

stocksucks

New Member
May 23, 2012
32
0
0
Portugal
Build on standby, feeling lazy about it.
I still havent decided the trans setting. Probably 11T on engine shaft to 18T input on jackshaft, to 11T output on the clutch to a 35 or 44T final. Then I'll mess with the cluth's springs...
Keep it up
 
wolf-jr

wolf-jr

New Member
Feb 17, 2012
50
2
0
Culver City
That bike looks awesome. So cool how its so low and I like the ratrod look to it.
Great job and I can't wait to see it running!
 
D

dmb

Active Member
Dec 4, 2010
1,354
3
36
lakewood ca
make a sleeve out of your sprocket and use a 1'' dia clutch or weld a clutch to your sprocket or machine a 3/4''-5/8'' + keyway on the crank or use a belt with a idler as a clutch
 
stocksucks

stocksucks

New Member
May 23, 2012
32
0
0
Portugal
@wolf: thanks for the compliments. I took a scale image from a H-D BTR from the internet, and assuming that it rode on 26" wheels, deduced the remaing parts size, so I guess that the overall look resembles a real BTR. I also like the ratty look.

@DMB: thanks for helping. I asked about machining the shaft, but it will make me take apart the engine. I don't wanna do that. I'll have a hard time replacing any part that might be broken during the process. Welding the clutch to the sprocket is an option I'll have to consider. The belt option is the one that I like most. I just don't know if while running and having to stop suddenly, disengaging the clutch via a lever won't take too long... Is there a video you know of that shows a similar setting at work?

@Daredevil: PM sent!
 
N

Nikita Gatsuts

New Member
Oct 6, 2012
4
0
0
Cascais, Lissbon, Portugal
Hi @stocksucks!!!

I live in portugal too!!!
i'm also truing to build a boardtracker out of my beach cruiser, but i can't use big engine because i don't have license to drive a motorcycle. Instead I'm thinking about building a motorized bicycle.

Where do you live?
 
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Velodrome

Velodrome

Well-Known Member
May 27, 2011
2,387
271
63
Phoenix-ish
Ok Stock. Give up the details on that AWSOME kill switch! Very authentic and period correct! Were did you find the parts? I would love to put one of these togather on my BTR which Im now gonig back to complete. PS: Love the rest of the build aswell, Great motor choice! Hey trukd ! You seeing this?
 
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